SW9/1200's were part of a series of switchers similar in appearance produced by the Electro-Motive Division of General Motors starting in mid-1930's.Although the colorful road units recieved more pubicity, these switchers were among the first widely accepted diesel locomotives.
The welded frame SW9 and 1200 provided 1200 horsepower and the ability to negotiate tight curves.Their light weght and small size made them perfect for yard swicthers, although they could sometimes be seen doing road work as well. The popularity of these units kept them in production from 1951 thrrough 1966, and some can still be seen switching in yards today.